13-PARAFAC decomposition of evoked potentials in patients treated by STN DBS

The effect of STN DBS (Deep Brain Stimulation of Subthalamic Nucleus) on the somatomotor network may differ from the effects on the cognitive networks ( Rektor et al., 2015 ). Thus, we acquired high-density (HD) scalp EEG data from 10 Parkinson’s disease patients with STN DBS during DBS ON and OFF state while performing 3-stimulus visual oddball task and we employed blind 3-way decomposition method called PARAFAC. We performed PARAFAC on 3-way data array ( Morup et al., 2008 ) composed by preprocessed averaged trials from all patients, both states (DBS ON/OFF) and all stimulus types. The resulting estimated PARAFAC components have 3 signatures - topography, time series and trial strength loadings for particular averaged trials. Finally, we compared loadings between trial types during both states by Wilcoxon test. PARAFAC revealed evoked activity which showed significant difference between loadings of frequent and target stimuli in the DBS ON state and no difference in DBS OFF. We transformed the topography of the component into the source space, which points to areas of the fronto-parietal attention network. PARAFAC decomposition of evoked potentials seems to be a helpful exploratory tool for HD EEG data. Our results also support a hypothesis that the DBS improves not only motor control but also affects cognitive networks. Acknowledgement: The research was supported by AZV grant 16-33798A and by CF MAFIL of CEITEC (supported by the CzechBI large RI project LM2015062, MEYS CR).